This invention relates to doorbells.
More particularly, the invention pertains to a doorbell response system which can be retrofit in an existing doorbell system without requiring the incorporation of new wiring in the existing doorbell system.
In a further respect, the invention pertains to a doorbell-telephone intercom system which can be utilized in conjunction with an existing doorbell and telephone(s) in a residence.
The use of an intercom system in a residence is well known in the art, with intercoms often being provided at the front door of the residence so that the inhabitants of the residence can converse with a visitor standing outside at the front door. The intercom includes a microphone for receiving verbal communications from the visitor standing at the front door, and includes a speaker for audibly relaying to the visitor comments made by the inhabitants of the residence.
In one such prior art system, the speaker and microphone are wired to a digital signal processor. The digital processor is spliced into the wiring leading from the doorbell button to the doorbell of the residence. The digital processor is also connected to a Public Switched Telephone Network (PSTN) just as if the digital processor were an ordinary telephone. When the doorbell button is actuated by a visitor standing at a door of the residence, the digital processor waits a predetermined length of time for a telephone in the residence to go off hook. If the residence phone is taken off hook by an inhabitant of the residence, then the phone is, without utilizing the PSTN, connected to the intercom to permit the inhabitant to speak to the visitor. If the residence phone does not go off hook, then the digital processor autodials a number over the PSTN to a remote telephone located outside the residence. See, for example, U.S. Pat. No. 4,764,953 to Chern et al. The use of a local or remote telephone to communicate with an intercom at the door of a residence is well known in the art. Although intercom-telephone systems are widely utilized in the art, such systems often have long standing disadvantages. First, the circuitry and/or components associated with such intercom-telephone systems is often complicated and requires the use of specialized telephony or other components. Second, prior art systems typically require the cutting or splicing of existing wiring and circuitry, making the retrofitting of such systems impractical. Once a residence has been constructed and the telephone and doorbell lines installed, most homeowners are not inclined to attempt to incorporate new wiring or system components in a wall. Third, while autodialing is a known feature of doorbell-intercom systems, such systems do not give a visitor the flexibility of selecting to leave a message or to communicate with the inhabitants of a residence. Fourth, prior art systems do not enable a visitor the ability to communicate over the PSTN with an inhabitant of the residence on every phone in the residence.